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聚(N-异丙基丙烯酰胺)(PNIPAM)具有独特的相变行为,已成为人们研究蛋白质折叠等生命过程发生机理的模型体系.我们利用基于原子力显微镜(AFM)的单分子力谱技术(SMFS)研究了单链PNIPAM在硫酸钠诱导下的相转变过程,并定量化了相变后所形成塌缩结构的稳定性.通过对单链PNIPAM的单分子力谱实验得知:在相变前,得到单调上升的力曲线,对应着PNIPAM无规线团结构的形变过程;相变后,得到的锯齿型力曲线,对应着PNIPAM塌缩结构在外力诱导下的解折叠过程.首次从单分子水平观察到在外加盐的作用下,单链PNIPAM低温相转变和高温相转变的差异:相比于低温相转变,高温相转变生成的塌缩结构更加稳定.
Poly (N-isopropylacrylamide) (PNIPAM) has a unique phase transition behavior and has become a model system for the study of the pathogenesis of protein folding and other processes.We used single molecule force spectrum based on atomic force microscopy (AFM) SMFS) was used to study the phase transition of single-stranded PNIPAM induced by sodium sulfate and to quantify the stability of the collapsed structure formed by phase transition.According to the single-molecule force spectrum of single-stranded PNIPAM, , The monotone ascending force curve is obtained, which corresponds to the deformation process of the PNIPAM random coil structure. After the phase change, the sawtooth-shaped force curve corresponds to the unfolding process of the PNIPAM collapse structure under the external force. At the molecular level, the difference between the low-temperature phase transitions and the high-temperature phase transitions of single-stranded PNIPAMs was observed under the action of added salt: the collapsed structure produced by high temperature phase transformation was more stable than the low temperature phase transitions.